This isn't correct. Chernobyl was a steam explosion but it's literally not possible for any nuclear power plant to ever have a true nuclear bomb type explosion. That's a trope straight out of the Simpsons. Chernobyl was just about the worst case scenario in terms of reactor stability combining a positive void coefficient, moderator tipped control rods, a Xenon saturated reactor core, almost all control rods removed, and no containment structure to top it all off. As far as "a very small portion of nuclear fuel" being leaked, that steam explosion completely removed the reactor hall above it. It's not like it was just the lid that flew off, the remains of the fuel bundles and graphite moderators were scattered for miles. The graphite left in the crater where the reactor used to be was all burning for days spreading any fission products contained inside up with the smoke.

Chernobyl was the worst case disaster. Even before Chernobyl happened nuclear power plants outside of the USSR were already using much much safer designs. Ultimately Chernobyl has killed more people due to fears around nuclear power than even the highest realistic death toll from the accident itself.